Abstract

Melanoma, the deadliest form of skin cancer, has long been a major focus of immunotherapy. Adoptive T cell therapy-based cancer immunotherapy has been used to enhance the specificity and potential of host immune system to treat melanoma. However, the infiltration and antitumor function of cytotoxic T cells (CTLs) are blocked or down-regulated by various signals derived from tumor cells and cells in tumor microenvironment. A novel approach to specify and enhance the homing ability of CTLs to tumor is of high demand. Interleukin-4 receptor (IL-4R) is over-expressed on many types of cancer cells, including melanoma, and has been widely employed for targeted drug delivery. In this work, we examined whether the tumor homing efficiency and anti-tumor therapeutic efficacy of CTLs could be heighten by labeling CTLs with IL4RPep-1, a targeting peptide that binds to IL-4R. The labeling was empowered by conjugating IL4RPep-1 with Dioleylphosphatidylethanolamine-biological anchor for membrane (DOPE-BAM), an oleyl acid-derived membrane anchor that incorporates into lipid membrane of cells. Tumor-specific CTLs isolated from the mice immunized by irradiated B16F10 melanoma cells were highly populated with CD62L+CD44+ activated T cells. After labeling with IL4RPep-1 via DOPE-BAM, CTLs were still functionally active, as determined by intracellular interferon-γ and granzyme release assays. Moreover, such labeling did not affect the proliferation of T cells. Adoptive transfer of IL4RPep-1-labeled, IL-4R-targeted CD45.1+CTLs into CD45.2 mice bearing B16F10 melanoma enhanced their accumulation at tumor compared to that of unlabeled T cells. Tumor homing of IL4RPep-1-labeled T cells was further validated by in vivo fluorescence imaging of mice bearing 4T1 tumor at mammary gland. Adoptive transfer of IL-4R-targeted CTLs showed remarkable anti-tumor growth activity in mice bearing B16F10 tumor compared to untargeted CTLs. After the transfer, flow cytometric study of immune cells showed significant increase of CD8+ T cells and F4/80+CD86+M1-polarized macrophages with noticeable decrease in tumor-promoting immune cells, such as F4/80+CD206+M2-polarized macrophages, Gr1+CD11b+ myeloid derived suppressor cells, and CD3+CD4+ T cells. The CTLs accumulated at tumor were mostly exogenous CD45.1+ T cells. These results implicate that IL-4R-targeted CTLs, which is enabled by labeling of with IL4RPep-1, can be a promising strategy in the field of adoptive T cell therapy against IL-4R-overexpressing tumor.